Conventionally, a gasification facility has been developed which uses as fuel a raw material such as coal, biomass or tire tips to produce a gasification gas.
FIG. 1 shows an example of a gasification facility under development comprising a gasification furnace 2 which has a fluidized bed 1 of bed material (such as silica sand or limestone) formed by vapor to gasify a raw material (such as coal, biomass or tire tips) fed to thereby produce a gasification gas and a flammable solid content, a combustion furnace 5 which is fed with the flammable solid content produced in the gasification furnace 2 together with the bed material through a guide pipe 3 and which has a fluidized bed 4 formed by fluidizing gas such as air or oxygen to burn the flammable solid content, a material separator 8 such as a hot cyclone which separates the bed material from a combustion gas guided through a combustion gas pipe 6 from the combustion furnace 5 and feeds the separated bed material through a downcomer 7 to the gasification furnace 2, a material separator 9 such as a hot cyclone which separates the bed material from a gasification gas produced in the gasification furnace 2 and a recovery receptacle 10 which recovers the bed material separated by the separator 9.
In FIG. 1, reference numeral 11 denotes a dispersion plate which allows the vapor guided into a bottom of the gasification furnace 2 to be uniformly blown up into the fluidized bed 1; 12, a partition wall which covers a part in the gasification furnace 2 connected with the guide pipe 3 in such a manner that only a lower portion of the part is opened to thereby prevent outflow of the gasification gas in the gasification furnace 2 through the guide pipe 3 into the combustion furnace 5 and prevent inflow of the fluidizing gas such as air or oxygen in the Combustion furnace 5 through the guide pipe 3 into the gasification furnace 2; 13, a dispersion plate which allows fluidizing gas guided into a bottom of the combustion furnace 5 to be uniformly blown up into the fluidized bed 4; and 14, a forced draft fan for forced feeding of the fluidized gas into the gasification and combustion furnaces 2 and 5.
In the above-mentioned gasification facility, during a normal operation, the fluidized bed 1 is formed in the gasification furnace 2 by the vapor. Feeding of a raw material such as coal, biomass or tire tips into the fluidized bed causes the raw material to be vapor-gasified to thereby produce a gasification gas and a flammable solid content. The flammable solid content produced in the gasification furnace 2 is guided through the guide pipe 3 together with the bed material into the combustion furnace 5 with the fluidized bed 4 formed by the fluidizing gas, and the flammable solid content is burned therein. The combustion gas from the combustion furnace 5 is guided through the combustion gas pipe 6 to the material separator 8 such as a hot cyclone where the bed material is separated from the combustion gas. The separated bed material is returned through the downcomer 7 to the gasification furnace 2 and is circulated.
In this respect, the bed material high-temperatured due to the combustion of the flammable solid content in the combustion furnace 5 is guided through the combustion gas pipe 6 together with the combustion gas, is separated by the material separator 8 and then is fed through the downcomer 7 to the gasification furnace 2, so that the gasification furnace 2 is kept hot and the produced gas by pyrolysis of the raw material and the raw material residue are reacted with the vapor to bring about aqueous gasification reaction [C+H2O=H2+CO] and hydrogen transfer reaction [CO+H2O=H2+CO2] to thereby produce a flammable gasification gas such as H2 or CO.
From the gasification gas produced in the gasification furnace 2, the bed material is separated by the material separator 9 such as hot cyclone. The bed material separated by the separator 9 is recovered by the recovery receptacle 10.
Incidentally, upon heat lack during a normal operation in the gasification facility, i.e., when heat for sufficient gasification of the raw material is unavailable in the gasification furnace 2, fuel such as coal, biomass or tire tips similar to the raw material fed to the gasification furnace 2 is supplementarily fed into the combustion furnace 5 for combustion so as to supplement lack of heat as shown by imaginary line in FIG. 1. Moreover, during preparative circulating preheating operation before the normal operation in the gasification facility, no raw material is fed into the gasification furnace 2, and not vapor but fluidizing air is fed to the gasification furnace 2 from below; in this state, the fuel such as coal, biomass or tire tips is fed for preheating into the combustion furnace 5 for combustion of the same as shown in imaginary line in FIG. 1, so that the bed material in the combustion furnace 5 high-temperatured due to the combustion of the fuel is guided through the combustion gas pipe 6 together with the combustion gas, is separated by the material separator 8 and is fed through the downcomer 7 to the gasification furnace 2, whereby circulating preheating is conducted in the gasification facility.
State-of-the-art technology for a gasification facility with gasification and combustion furnaces 2 and 5 as shown in FIG. 1 is disclosed, for example, in Patent Literature 1.
[Patent Literature 1] JP 2007-112872A